This is my absolute favorite way to eat dark leafy greens, and has been a favorite for everyone I have served it to. It works equally well with turnip greens, kale, collard greens, or mustard greens.
For me, the key to making dark leafy greens palatable is to cook them until tender. In my opinion, most recent cookbooks greatly underestimate cooking time. Steam kale for 5 minutes and it will be the texture of shoe leather; stew it for 30-45 minutes and it is soft and delicious.
Pre -cook the potatoes in their skins, in boiling salted water for about 25 minutes. I find that the texture improves if you cook them in advance and refrigerate them.
Simmer the greens in the water with salt for about 30 minutes - Kale may need a bit more time, mustard greens a bit less.
Saute the chilis, garlic and ginger in the oil and butter mix until the chilis and garlic both darken. Chop and add the potatoes, and coarsely mash them with a fork. Drain the cooked greens and stir them in. Add lemon juice just before serving.